We study resonant production of pairs of Standard Model (SM-)like Higgs bosons, in the presence of new neutral Higgs states together with new colored scalars (stops or sbottoms) in loops within the Next-to-Minimal Supersymmetric Standard Model. This is used as a test case to prove that the Large Hadron Collider has sensitivity to a variety of effects stemming from interferences between resonant (heavy) Higgs diagrams and/or among these and nonresonant topologies involving loops of both tops and stops. These effects can alter significantly the naive description of individual <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>s</mi></mrow></math>-channel Breit-Wigner resonances, leading to distortions of the latter, which, on the one hand, may mask their presence but, on the other hand, could enable one to extract features of the underlying new physics scenario. This last aspect is made possible through a decomposition of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>g</mi><mi>g</mi><mo stretchy="false">→</mo><mi>h</mi><mi>h</mi></math> signal process into all its amplitude components, each of which has a well-defined coupling structure. Ultimately, such effects can be traced back to the relevant Feynman diagrams and can enable a detailed interpretation of this process. To illustrate this, we introduce various benchmark points that exhibit potentially observable features during the current and/or upcoming runs of the LHC in one or more of the three customary di-Higgs decay channels: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><msup><mi>τ</mi><mo>+</mo></msup><msup><mi>τ</mi><mo>−</mo></msup></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><mi>γ</mi><mi>γ</mi></math>.

United Kingdom

Sweden

Stefano Moretti

Italy

Luca Panizzi

Jörgen Sjölin

Harri Waltari

Deconstructing resonant Higgs boson pair production at the LHC: Effects of colored and neutral scalars in the NMSSM test case

We investigate the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ϕ</mi><mrow><mn>2</mn><mi>n</mi></mrow></msup></math> deformations of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">O</mi><mo stretchy="false">(</mo><mi>N</mi><mo stretchy="false">)</mo></mrow></math>-symmetric (generalized) free theories with a flat boundary, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>n</mi><mo>≥</mo><mn>2</mn></math> is an integer. The generalized free theories refer to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mo>□</mo><mi>k</mi></msup></math> free scalar theories with a higher derivative kinetic term, which is related to the multicritical generalizations of the Lifshitz type. We assume that the (generalized) free theories and the deformed theories have boundary conformal symmetry and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">O</mi><mo stretchy="false">(</mo><mi>N</mi><mo stretchy="false">)</mo></mrow></math> global symmetry. The leading anomalous dimensions of some boundary operators are derived from the bulk multiplet recombination and analyticity constraints. We find that the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ε</mi><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></math> expansion in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ϕ</mi><mn>6</mn></msup></math>-tricritical version of the special transition extends to other multicritical cases with larger odd integer <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>n</mi></math>, and most of the higher derivative cases involve a noninteger power expansion in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ε</mi></math>. Using the analytic bootstrap, we further verify that the multiplet-recombination results are consistent with boundary crossing symmetry.

China

Yongwei Guo

Wenliang Li

Boundary anomalous dimensions from BCFT: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">O</mi><mo stretchy="false">(</mo><mi>N</mi><mo stretchy="false">)</mo></mrow></math>-symmetric <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ϕ</mi><mrow><mn>2</mn><mi>n</mi></mrow></msup></math> theories with a boundary and higher-derivative generalizations

We propose a quantum mechanical theory of quantum spaces described by large <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> noncommutative geometry as a model for quantum gravity. The model admits a fuzzy sphere as a static solution. Over the fuzzy geometry, the quantum mechanics of the fermions is given by a sum of oscillators with equal frequency. The energy state where exactly half of the Fermi sea is filled contains the maximal amount of degeneracy. This state of the fuzzy sphere obeys the mass-radius relation of a Schwarzschild black hole if the fuzzy sphere is identified with the black hole horizon. Moreover, the set of states in the Fermi sea gives precisely the Bekenstein-Hawking entropy. We thus propose that quantum black holes are described by fuzzy spheres with a half-filled Fermi sea in our model. We also consider a system of two fuzzy spheres by embedding them as blocks in the matrix quantum mechanics. When the distance <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>r</mi></math> between the two fuzzy spheres is small, the total energy of the system can be computed using perturbation theory. We show that, in the leading order of large <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> limit, the interaction energy depends on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>−</mo><mi>G</mi><msub><mi>M</mi><mn>1</mn></msub><msub><mi>M</mi><mn>2</mn></msub></math> exactly in the manner as in Newton gravity. To reproduce the correct <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>r</mi></math> dependence in the long range, we expect the inclusion of large <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> corrections and quantum effects will be needed.

Taiwan

Chong-Sun Chu

Matrix model proposal for quantum gravity and the quantum mechanics of black holes

The three Standard Model neutrinos can have Majorana mass or strictly Dirac mass, but both scenarios are practically indistinguishable in neutrino oscillation experiments. If they are pseudo-Dirac, however, there will be new mass splittings among the pseudo-Dirac pairs, potentially leaving traces in neutrino oscillation phenomena. In this work, we use flavor ratios of astrophysical neutrinos to discriminate different possible mass spectra of pseudo-Dirac neutrinos. We show that it will be possible to impose robust bounds of order <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>δ</mi><msubsup><mrow><mi>m</mi></mrow><mrow><mn>3</mn></mrow><mrow><mn>2</mn></mrow></msubsup><mo>≲</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>12</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>eV</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math> on the new mass squared splitting involving the third pseudo-Dirac mass eigenstates (those with the least electron flavor composition) with the future experiment IceCube-Gen2. The derived sensitivity is robust because it only assumes an extragalactic origin for the astrophysical neutrinos and hierarchical pseudo-Dirac mass spectrum. In case the neutrino sources are known in the future, such bounds can potentially improve by up to five orders of magnitude, reaching <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>δ</mi><msubsup><mi>m</mi><mn>3</mn><mn>2</mn></msubsup><mo>≲</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>17</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mi>eV</mi><mn>2</mn></msup></math>.

Brazil

Chee Sheng Fong

Yago Porto

Constraining the pseudo-Dirac nature of neutrinos using astrophysical neutrino flavor data

Simultaneous measurement of mass and radius with high precision is essential to unravelling the equation of state of matter at the core of neutron stars. Measurement of massive pulsars indicates that they have to be stiff at low densities. In this work, an ensemble of agnostically constructed equations of state was studied for the mass-radius measurement. The radius of neutron stars obtained from the ensemble was confined within a 10.5–14.5 km bound. Among the NICER measurements, PSR J0437–4715 provides the most stringent constraint on the equation of state. It was found that the detection of stars with smaller radii would prefer a softer equation of state, and the detection of stars with larger radii would prefer a stiffer equation of state. However, irrespective of the detection of stars with a smaller or larger radius, the sound speed peak indicates that stars are likely to have a smooth phase transition at a few times saturation densities, and the matter at the core may not be pure conformal quark matter. A better precision of the radius measurement drastically increases the chances of constraining the equation of state. The equation of state would be more effectively constrained if the measurement of large-radius stars with high precision were to happen. Precise radius measurements of neutron stars with smaller radii provide limited constraints on the equation of state over the density range relevant to neutron stars, largely independent of the stellar mass. Also, measurements for different masses are necessary to constrain the equation of state at all density ranges relevant to neutron stars.

India

Asim Saha

Ritam Mallick

The prospect of confining the equation of state of neutron stars with future mass and radius measurements

In this paper, we investigate the thermodynamical and optical characteristics of a black hole surrounded by massive spin-1 vector fields in the framework of Kaluza–Klein gravity. Motivated by the natural emergence of massive vector fields through the dimensional reduction of higher-dimensional gravity, we explore their role in modifying the near-horizon physics and observable signatures of black holes. These vector fields, akin to dark photons, introduce Yukawa-like corrections to the gravitational potential and mimic dark matter effects without invoking exotic particles. Our thermodynamic analysis, extended via logarithmic-corrected Barrow entropy, reveals that these fields significantly alter black hole temperature, specific heat, and Gibbs free energy. Notably, phase transitions are identified and confirmed using thermodynamic geometry tools, including Quevedo and HPEM metrics, highlighting the presence of stable remnants under quantum gravity corrections. Furthermore, we examine accretion disk structures and black hole shadow images through ray-tracing techniques under both static and infalling spherical accretion models. The direct and secondary images of the disk, as well as photon ring features, exhibit distinct deformations based on $$\gamma $$ and $$\lambda $$ . These modifications affect observable properties such as shadow size, intensity profiles, and lensing behavior, suggesting potential avenues for empirical testing via black hole imaging. Our findings underscore the rich phenomenology induced by massive vector fields in KK gravity, providing a unified perspective on black hole thermodynamics, dynamical stability, and observational signatures.

Saudi Arabia

Ali Koam

Azerbaijan

Pakistan

Shahid Chaudhary

Uzbekistan

Farruh Atamurotov

Ali Ahmad

Ibtisam Masmali

Probing Kaluza–Klein black holes with massive vector fields via thermodynamics, shadows, and accretion disks

The Cabibbo–Kobayashi–Maskawa matrix element $$|V_{\textrm{cb}}|$$ is an important Standard Model parameter, whose value can be determined by using the semi-leptonic decay $$B\rightarrow D^{*}\ell {\bar{\nu }}_\ell $$ . The perturbative QCD (pQCD) corrections to the $$B \rightarrow D^{*}$$ transform form factor $${{\mathcal {F}}}(w)$$ has been known up to the $$\hbox {N}^3$$ LO level, whose magnitude remains sensitive to the choice of renormalization scale $$\mu _r$$ . To improve the precision of $${{\mathcal {F}}}(w)$$ and hence $$|V_{\textrm{cb}}|$$ , we first apply the single-scale approach of Principle of Maximum Conformality (PMC) to eliminate the conventional (Conv.) renormalization scale dependence of the short-distance parameter $$\eta _A$$ and then predict the contribution of its unknown $$\hbox {N}^4$$ LO term via Bayesian analysis. In this paper, we adopt two probabilistic models for Bayesian analysis: the Cacciari–Houdeau model (CH model) and the geometric behavior model (GB model). It is shown that by using the PMC series in combination with Bayesian analysis, one can achieve high degree of reliability in estimating unknown higher-order terms. A more convergent behavior is achieved by applying the PMC, confirmed by the predicted $$\hbox {N}^4$$ LO contributions: for the CH model, $$\eta _A|_{\mathrm{Conv.}}^{\text {N}^{4}\text {LO}}=\{-\,0.0032,+\,0.0052\}$$ and $$\eta _A|_{\textrm{PMC}}^{\text {N}^{4}\text {LO}}=\{-\,0.0004,+\,0.0004\}$$ ; for the GB model, $$\eta _A|_{\mathrm{Conv.}}^{\text {N}^{4}\text {LO}}=\{-\,0.0049,+\,0.0075\}$$ and $$\eta _A|_{\textrm{PMC}}^{\text {N}^{4}\text {LO}}= \{-\,0.0007,+\,0.0007\}$$ . Comparing with the latest experimental measurements, we obtain $$|V_{\textrm{cb}}||_{\textrm{PMC}}=(40.58^{+0.53}_{-0.57})\times 10^{-3}$$ , which is consistent for both CH and GB models and in good agreement with the PDG world average, $$|V_{\textrm{cb}}|_{\textrm{PDG}}=(41.1\pm 1.2)\times 10^{-3}$$ within errors.

Wang Li

Xing-Gang Wu

Hua Zhou

Xu-Chang Zheng

Determination of $$|V_{\textrm{cb}}|$$ using Bayesian analysis of the $$B \rightarrow D^{*}\ell {\bar{\nu }}_\ell $$ semileptonic decay width with four-loop QCD corrections

Progress in the theoretical understanding of parton branching dynamics within an expanding Quark Gluon Plasma relies on detailed and fair comparisons with experimental data for reconstructed jets. Such comparisons are only meaningful when the computed jet, be it analytically or via event generation, accounts for the complexity of jets reconstructed in the challenging environment of heavy-ion collisions. Jet reconstruction in heavy-ion collisions involves a necessarily imperfect subtraction of the large and fluctuating underlying event: reconstructed jets always include underlying event contamination. To identify true jet quenching effects, modifications due to the interaction of the branching partonic system with the Quark Gluon Plasma, we establish a baseline that accounts for possible background contamination on unmodified jets. In practical terms, jet quenching effects are only those not present in jets produced in proton-proton collisions that have been embedded in a realistic heavy-ion background and where subtraction has been carried out analogously to that in the heavy ion case. With this setup, we assess the sensitivity to underlying event of commonly discussed jet quenching observables and its impact on the robustness of Machine Learning studies, aimed at classifying jets according to their degree of modification by the Quark Gluon Plasma, that rely on those observables. We find the discrimination power of a simple Boosted Decision Tree to be robust in the realistic scenario where both medium response and underlying event are present, giving support to portability to the experimental context.

Portugal

J. Gonçalves

J. Milhano

Apples to apples in jet quenching: robustness of Machine Learning classification of quenched jets to underlying event contamination

We develop a framework based on the full one-loop finite-temperature effective potential model, within which the bubble wall velocity is calculated using the local thermal equilibrium (LTE) approximation, and the kinetic energy fraction $\textit{K}$ is computed directly. In cosmological phase transitions, these quantities play a critical role in determining the resulting gravitational wave signals. Using the xSM as a benchmark model, we compute the peak gravitational wave spectra under different methods for determining the wall velocity and the kinetic energy fraction $\textit{K}$, and compare these results to those obtained using the commonly employed bag model. Within the scanned parameter space, we find: (1) Deflagration is the most prevalent mode of fluid motion.(2) Gravitational wave spectra based on the full effective potential with LTE-derived wall velocity and integrated $\textit{K}$ can differ significantly from those using the bag model with fitted $\textit{K}$. In the deflagration regime, discrepancies reach up to 48% in peak frequency and 90% in amplitude. (3) The bag model provides a good approximation to the full equation of state in many cases. Notably, in deflagration scenarios with input wall velocity, the gravitational wave spectra obtained from the bag model more closely resemble the LTE-based results than those derived using the full potential with this input wall velocity ( ).

Zongguo Si

Hongxin Wang

Lei Wang

Yang Xiao

Yang Zhang

The bubble wall velocity in local thermal equilibrium and energy budget with full effective potential

Modular flavor symmetries have been proposed as a new way to address the flavor problem. It is known that they can emerge from string compactifications. We discuss this connection in detail, and show how the congruence subgroups of SL(2$\textit{,}$ ℤ), which underlie many modular flavor symmetries, emerge from stringy duality symmetries by orbifolding. This requires an analysis of massive states, which reveals a picture that is more intricate than the well-known situation on the torus. It involves towers of states of different quantum numbers, related by modular transformations. Members of different towers become massless at different points in moduli space. We also show that, at least in the ℤ orbifold, the string selection rules can be understood as discrete remnants of continuous gauge symmetries. Non-Abelian discrete flavor symmetries arise as relics of various, relatively misaligned, continuous Abelian gauge symmetries. The generators of these U(1) symmetries give rise to $$ \mathcal{CP} $$ -violating Clebsch-Gordan coefficients. If the modulus settles close to a critical point, the corresponding gauge bosons may be light enough to be searched for at future colliders.